President Bush, so far, has shown little leadership on climate change. This was not changed when he publicly acknowledged climate change in his January State of the Union address. Will Angela Merkel fill the gap? As German chancellor, she holds European Union presidency until the end of June and G8 presidency until the end of the year. During these twin presidencies, she can influence many events that might be crucial to the future of climate change.

In March, she will chair the spring summit where EU heads of government will make major decisions on the future of climate and energy security policies. The European Commission has proposed that the EU accept as unilateral greenhouse-gas-reduction targets of a 20 percent decrease by 2020 (from 1990 greenhouse-gas levels) and, if other industrialized countries agree to an even more ambitious course, a 30 percent target.

The commission further proposes that by 2020 energy efficiency in the EU should be increased by 20 percent, and renewable energy should account for 20 percent of energy used. Many EU countries have difficulties in accepting one target or the other, but at the moment Merkel seems to be determined to push the entire package through. This would set the EU on a path that would prove the choice between economic growth and a stable climate is a false one.

In April, at the transatlantic EU-U.S. summit where climate and energy security will top the agenda, Merkel will try to set the stage for a global energy efficiency technology initiative by exacting commitments from the G8 members to meet energy goals. She knows that the struggle against climate change cannot be won without the support of the United States, which has the biggest innovation potential in the world. The initiative could be launched at the next G8 summit, scheduled to take place in Germany in June.

The five big emerging countries -- including China, which is second only to the United States in the amount of greenhouse-gas emissions -- have been invited to this G8 summit. Based on progress made at two earlier meetings, the plan is to gain acceptance for a substantial mandate to negotiate a far-reaching agreement. Even the idea of a special U.N. General Assembly meeting on climate change in September is gaining momentum -- and Merkel supports that. If that doesn't happen, there will be a U.N. climate summit in Bali in December, when Merkel is still head of the G8.

If any international leader can take the lead in the global climate debate, Merkel can -- or certainly has the opportunity to do so. As a physicist and the former minister of environment who negotiated the Kyoto Protocol for Germany, she knows that the basic science of climate change is no longer in dispute. She also knows that the scale and urgency of the challenge the world faces is worse than originally feared. And that tackling climate change is an imperative, not a choice; a problem for today, not tomorrow.

Merkel, however, is leader of the Christian Democratic Party, which largely listens to industry. Last summer, she laid the cornerstone for the biggest lignite coal power plant in the world in western Germany. In the last few weeks, she supported the German auto industry's call to waterdown carbon-dioxide reduction targets proposed for the car industry.

On the other hand, increasingly, industry, banks and insurers are urging her to take climate change seriously, and open the door to the next industrial revolution. The German public, likewise, is calling for serious steps to slow climate change.

Nearly 18 years ago, Merkel, who was raised in the former East Germany, learned that the Berlin Wall, built to last for an eternity, could come down surprisingly quickly. Today, Merkel is up against the wall that blocks progress in the climate debate. She has jumped over several walls on the way to become Germany's chancellor. Will she jump over this wall, too?